English actually has all the relevant sounds in most dialects so I will try to explain in it reference to that. Most English dialects have environments where consonants are reliably aspirated, or not, depending on their voicing and surrounding environment. Unvoiced stops (p/t/k) in isolation "pat" or "cap" are moderately aspirated. Voiced stops (b/d/g) are not like "dog" or "bad". (Leaning on this pattern as a partial hack using a feature common in a lot of European languages, is why p and b are what they are in Pinyin, and many other Chinese romanizations.)
In principle, if your dialect does not have a length contrast for /æ/ after a voiced consonant (many do though including mine, making the vowel longer in that environment, so you'll have to try to say them with equal vowel length) then "pap" and "bab" (to rhyme with cap and cat) when whispered (no vocal chord movement, so all equally unvoiced) should be differentiated only by aspiration similar to Mandarin's p/b difference. Though aspiration is Mandarin is a bit more forceful.
As an aside, most people can hear the difference between those words when whispered, hearing a voiced or unvoiced consonant, based solely on the aspiration hint. Phonetic interpretation is a strange and subtle thing. And voicing in Mandarin? It plays the inferior role to aspiration's main starring role, a role reversal of the English arrangement.
Some languages, such as Hindi, have both the voiced/unvoiced and aspirated/unaspirated distinction, so they have 4 consonants (/t d th dh/) where English only has two (/t d/).
Hindi also has retroflex equivalents of those 4 consonants, and there are minimal pairs between all 8 of them. A typical English speaker would struggle to tell the difference between them.
For these sorts of reasons, a Romanisation of names in different languages that (1) is easy to pronounce for English speakers, and (2) sounds like the word in the original language, is going to be a tall order.
[edit] ah, one (!) of the two "tell" audio recordings in that dictionary seems to pronounce it in a different way that would illustrate the aspiration, but that seems different to how I've usually heard 'tell' being pronounced.
A common way of illustrating aspiration is: hold a sheet of paper in front of your mouth (or your hand), as you say the words. "tell" will give you a noticeable puff of air as it leaves the mouth, as opposed to "stellar", which won't.
Maybe these recordings are helpful to you: https://en.wikipedia.org/wiki/Aspirated_consonant#Allophonic
Can't be done. The Roman alphabet is a pretty good alphabet for Latin, but it isn't for Chinese, which has different sounds than are in Latin (or English).
For example, stop consonants in English have a voiced-unvoiced distinction: /p b t d k g/
Latin is similar: /p b t d k g kw gw/
Chinese is totally different. Instead of a voiced-unvoiced distinction, it has aspirated-unaspirated: /p ph t th k kh/ (with the h denoting an aspirated stop).